Keywords: SPC, SPC control chart
SPC control chart is an important tool of statistical process control, control charts is a small microcosm of the entire production process, which passes the information to the quality management process, including the process is stable, the production capacity meets the requirements, if the process needs to be adjusted.
Process is a process to produce results, so in a sense, the severity of the process quality is often greater than the quality of the result.
SPC control chart is an important tool for process quality concerns, it will introduce the kind of precautions when SPC control chart has been applied.
First, the control and analysis control chart control
Depending on the use, the SPC control chart divided into two categories, i.e., analysis and control control control chart of FIG. The main object of the analysis is a control chart:
First, the analysis of the production process is in steady state. If the process is not at steady state, it should adjust the process so as to achieve steady state.
The second is the ability to analyze the process of the production process meets the technical requirements. If not satisfied, we need to adjust the process capability, so as to meet.
Belgian scholar Weierda call this state is the steady-state technology, while the former is a statistical steady state.
When the process has reached a state that we determined, the analysis can be extended as a control by control line control chart of FIG. Since the latter is equivalent to the production of Dafa, so by the former into the latter should be a formal handover procedures. Here the criteria to use to determine the steady state (referred to as stable judgment criteria), but also the criteria used to determine abnormalities before stabilizing (abbreviated sentence different criteria).
Application of controlling the control object is to make the production process of FIG maintained in the determined state. Application control control chart of the process, if the process took place in an exception should be performed "found different reasons, to take measures to ensure the elimination, is no longer present, the inclusion criteria." The process to restore the original state.
Analysis of the above-described embodiment of a control chart with control actually continuous quality improvement process of the control process of FIG.
InfinityQS --SPC control charts sentenced to different criteria
Second, the application control problems FIG SPC to consider
Control charts for where? In principle, any process, where the need for quality control management applications can control chart. However, here also called: the control object is determined - to be able to quantify the quality indicator, the measured value in order to control the application of FIG.
If only qualitative descriptions can be quantitatively rather, it can only be applied to control the count value of FIG. Process control must be repeatable, that has statistical laws. Controlled for only a one-time or a few times the process is clearly difficult to control chart.
如何选择控制对象?在使用控制图时应选择能代表过程的主要质量指标作为控制对象。一个过程往往具有各种各样的特性，需要选择能够真正代表过程 情况的指标。
例如，假定某产品在强度方面有问题，就应该选择强度作为控制对象。在电动机装配车间，如果对于电动机轴的尺寸要求很高，这就需要把机轴直径作为我们的控制对象。
盈飞无限SPC控制图
怎样选择控制图?选择控制图主要考虑下列几点：首先根据所控制质量指标的数据性质来进行选择；其次，要确定过程中的异常因素是全部加以控制(全控)还是部分加以控制(选控)，若为全控应采用休哈特图等；若为选控，应采用选控图。
如何分析控制图?如果控制图中点子未出界，同时点子的排列也是随机的，则认为生产过程处于稳态或控制状态。如果控制图中点子出界(或不出界)而点子的排列是非随机的(也称为排列有缺陷)，则认为生产过程失控。
对于点子出界或违反其他准则的处理。若点子出界或点子的排列是非随机的，则应立即追查原因并采取措施防止它再出现。
对于过程而言，控制图起着报警铃的作用，控制图点子出界就好比报警铃响，告诉现在是应该进行查找原因、采取措施、防止再犯的时刻了。
一般来说，控制图只起报警铃的作用，而不能告诉这种报警究竟是由什么异常因素造成的。要找出造成异常的原因，除去根据生产和管理方面的技术与经验来解决外，应该 强调指出，应用两种质量诊断理论和两种质量多元诊断理论来诊断的方法是十分重要的。
控制图的重新制定。控制图是根据稳定状态下的条件5M1E来制定的。如果上述条件变化，如操作员更换或通过学习操作水平显著提高，设备更新，采用新型原材料或其他原材料，改变工艺参数或采用新工艺，环境改变等，这时，控制图也必须重新加以制定。由于控制图是科学管理生产过程的重要依据，所以经过相当时间的使用后应重新抽取数据，进行计算，加以检验。
综上所述，SPC控制图的应用需要由分析用控制图向控制用控制图过渡，观察点子排列情况并进行分析，诊断过程质量。在一定时间后，对SPC控制图控制限作出相应的调整，或重新制定。
Reproduced in: https: //www.jianshu.com/p/070056a663f4